In the following description, a generally used paging group and an idle mode of a terminal are schematically explained.
FIG. 1 is a diagram illustrating a paging group in a general IEEE 802.16 system.
Referring to FIG. 1, a plurality of base stations (BS) supporting an idle mode belong to a paging group to construct a paging area.
In this case, the paging group indicates a logical group. If there is a traffic that targets a mobile station (MS), the object of the paging group is to provide a neighbor range area that can be paged in downlink (DL). And, the paging group should meet the condition to be large enough for a specific terminal to exist for most of time within a same paging group and the condition to be small enough for a paging load to maintain a proper level.
FIG. 1 shows four paging groups defined on multiple base stations located at hexagonal lattices. One base station is able to be included in one or more paging groups. The paging group is defined by a management system. And, a paging group is able to use a paging group-action backbone network message. Moreover, a list of terminal in idle mode is managed using a paging-announce message corresponding to one of backbone network messages and initial paging of all base stations belonging to a paging group can be managed.
Idle mode indicates an operation of supporting a terminal to periodically receive a downlink (DL) broadcast traffic transmission without registering at a specific base station when the terminal is moving in a wireless link environment constructed with multiple base stations.
Idle mode is able to give the benefit to a terminal by eliminating a handover-related activation requirement and general operation requirements. Idle mode is able to save power and operational resources used by a terminal in a manner of put limitation on a terminal action to be scanned in a discrete cycle.
Idle mode provides a simple and proper method of informing a terminal for a downlink traffic in pending and is able to give the benefit to a network and a base station by removing a wireless interface and a network handover (HO) traffic from an inactive terminal.
Hereinafter, an example of an operation procedure of a mobile station entering an idle mode in a general IEEE 802.16 system will be described with reference to FIG. 2.
Referring to FIG. 2, a mobile station can transmit a deregistration request (DREG-REQ) message to a serving base station to enter an idle mode from a normal mode (S201).
The serving base station which has received the DREG-REQ message can transmit and receive information of the mobile station and the serving base station to and from a paging controller. Namely, the serving base station can notify the paging controller of mobile station identifier (MSID) and serving base station identifier (BSID). Also, the paging controller can notify the serving base station of paging group identifier (PG ID) or paging controller identifier (PC ID). The paging group identifier or the paging controller identifier can be used to transmit and receive a paging message.
Subsequently, the serving base station can transmit a deregistration command (DREG-CMD) message to the mobile station. The serving base station can transmit the deregistration command (MOB_DREG-CMD) message to the mobile station in response to the deregistration request message. The deregistration command message can include paging information. At this time, the paging information can include parameters such as paging cycle, paging offset, and paging listening interval. The deregistration command message can further include paging controller identifier and paging group identifier (S203).
At this time, the paging information can be included in the deregistration command message in a type of Table 1 below. This information can be provided to the mobile station through a ranging response (RNG-RSP) message in a location update procedure which will be described later.
TABLE 1TypeLengthValueScope1347Bits #0-15: PAGING_CYCLE - cycle in which the pagingRNG-RSPDREG-message is transmitted within the paging group. BitsCMD   #16-31: PAGING_OFFSET - determines the frame within thecycle from which the paging interval starts. Shall be smallerthan PAGING_CYCLE value. Bits #32-47: Paging-group-ID -ID of the paging group the MS is assigned to. Bits#48-55: Paging Interval Length - Max duration in frames ofPaging Listening interval. Used in calculation of Paginglistening interval. value shall be between 1 and 5 frames(default = 2).  
The parameters in Table 1 are user equipment-specific values, and different paging cycles, paging offsets and paging listening intervals can be allocated to the respective mobile stations. The base station can identify a paging interval of each mobile station through the parameters.
The mobile station which has received the DREG-CMD message from the serving base station identifies that a request of entrance to an idle mode is successfully accepted, and enters the idle mode. The mobile station can receive a paging message based on paging information received through the MOB_DREG-CMD message. Namely, the mobile station can monitor a radio channel to identify the presence of a paging message transferred thereto for a paging listening interval. The mobile station is operated in a sleep mode (or the radio channel is turned off) for the other interval to reduce power consumption (S204).
A call or external packet can be transmitted to the paging controller (S205).
In this case, the paging controller can perform a paging procedure of the mobile station. At this time, the paging controller can transmit a paging announcement message to all base stations within the paging group (S206).
All the base stations within the paging group, which have received the paging announcement message, can broadcast a MOB_PAG-ADV message to all mobile stations managed by the base stations. At this time, the paging message can include parameters of Table 2 (S207).
TABLE 2Size (bit)Syntax    Notesfor (i = 0; i < Num_Paging_Group_IDs;——i++) {   Paging Group ID   —16}——Num_MACs   —Number of MS MAC addresses   For (j = 0; j < Num_MACs; j++) {   ——MS MAC Address hash   24The hash is obtained bycomputing a CRC24 on the MS48-bit MAC address. Thepolynomial for the calculation is0x1864CFB   Action Code   2Paging action instruction to MS0b00 = No action required 0b01 =Perform ranging to establishlocation and acknowledgemessage 0b10 = Enter network0b11 = Reserved   Reserved   6—}——Padding   variable   Padding bits to ensure octetaligned   TLV Encoded Information  variable   TLV-specific   }— 
The mobile station checks the MOB_PAG-ADV message. If the mobile station is paged by the paging controller, the mobile station enters a normal mode and is then able to perform communications with the serving base station (S208, S209).
In a general communication system, mobile stations belonging to the same paging group can have different paging intervals. These paging intervals can be managed by the paging controller or the base station. The paging intervals will be described with reference to FIG. 3.
FIG. 3 is a diagram illustrating different paging intervals of two different mobile stations, which belong to the same paging group in a general communication system.
Referring to FIG. 3, it is assumed that two mobile stations MS1 and MS2 exist in the same paging group. At this time, in the mobile station MS1, the first frame of the paging cycle can be established as a paging interval, and in the mobile station MS2, the fourth frame of the same paging cycle can be established as a paging interval.
Next, a procedure of updating system information in a mobile station which is in an idle mode will be described.
The mobile station which is in the idle mode wakes up for only a listening interval and then receives a paging message. Subsequently, the mobile station takes a corresponding action in accordance with an action code value. For example, if an action code corresponding to the mobile station is ‘0’, the mobile station does not take any action. If an action code corresponding to the mobile station is ‘1’, the mobile station can perform ranging for location update.
It is assumed that a downlink channel descriptor (DCD) message, an uplink channel descriptor (UCD) message or neighboring cell information transmitted from a preferred base station of the mobile station which is in the idle mode is updated. At this time, in a general wireless communication system, the preferred base station can notify the mobile station of a frame where a message containing the updated DCD/UCD or neighboring cell information is transmitted by transmitting a broadcast control pointer information element (Broadcast_Control_Pointer_IE) to the mobile station. Table 3 illustrates contents that can be included in the broadcast control pointer information element.
TABLE 3Size (bit)Syntax NotesBroadcast_Control_Pointer_IE(——) {   Extended DIUC   4Broadcast_Control_Pointer_IE( ) = 0xA   Length   4Length in bytes   DCD_UCD Transmission7The most significant bits of the frameFrame   number's least 9 significant bits of the nextDCD and/or UCD transmission.   Skip Broadcast_System_Update1— If (Skip——Broadcast_System_Update ==0) {   Broadcast_System_Update_Type1Shows the type of Broadcast_System_Update0: ForMOB_NBR-ADV Update 1: ForEmergency Services Message   Broadcast_System_Update7The least significant bits of the frame_Transmission _Frame   number of the nextBroadcast_System_Update transmission.   }——}——
Referring to Table 3, the broadcast control pointer information element can include information of a frame (DCD_UCD transmission frame) where the DCD/UCD messages are transmitted, and a frame (broadcast system_update_transmission_frame) for update of broadcast system information.
Unlike the mobile station which is in an active mode, the mobile station which is in the idle mode can receive a message by waking up for only a listening interval. Since the updated DCD or UCD message has a relatively great transmission cycle (maximum ten seconds), if the updated message is not transmitted within the listening interval of each mobile station, each mobile station may not receive the updated message. Such a case will be described with reference to FIG. 4.
FIG. 4 is a diagram illustrating an operation procedure of updating system information through a mobile station, which is in an idle mode, in a general communication system.
Referring to (a) of FIG. 4, the mobile station can receive the broadcast control pointer information element from the preferred base station for only its listening interval. The mobile station can wake up to receive the updated system information even if a frame indicated by the broadcast control pointer information element does not correspond to the listening interval of the mobile station. The mobile station can again sleep until next listening interval if the updated system information is successfully received.
However, it may be assumed that the mobile station fails to receive the updated system information from the frame indicated by the broadcast control pointer information element as illustrated in (b) of FIG. 4. At this time, the mobile station may have to receive system information by waking up until next interval where system information is transferred.